AusJustin,

I had the same problems as well and thanks to the guys here on the thread Ive been able to fix the problem, however you will need to face the fact that you will have to rebulid these diffs every 8 to 10 days at the track.

Just like WC said get the new rebuild kit, and what I did was use the old shims plus the new shims on the rebuild kit so I have two shims under each sun gear and remove the outside small shim on the outdrive that goes between the diff case and the outdrive. Use alot of green slime under the shims and around the diff case seals so the 5k oil lasts until the next rebuild.